The object of this invention is to provide apparatus for absorbing mechanical energy, in particular energy of very strong shocks. Such an apparatus is used for absorbing the energy of shocks in the rail and automotive vehicles, in the construction of cannons and rocket launches, etc., as a bump stop in elevators, travelling cranes, lifts and other mobile apparatuses and machine parts as well as a damper of vibrations arising during the travel of vehicles, running of machines and devices.
The apparatus of this invention is designed so as to perform simultaneously two or more of the above mentioned functions, e.g., absorb strong shock, damp vibration, and effect stoppage of moving vehicles.
The hitherto known apparatuses for absorbing memechanical energy are characterized by the fact that they have an exactly defined field of application at a strictly defined level of absorbed energy. When these levels of absorbed energy are exceeded, they do not carry out their function and become destroyed. At lower levels of absorbed energy they exhibit properties of an elastic solid and transmit the acting forces to the device onto which they are mounted. Due to these circumstances the hitherto known absorbers of the energy of shocks are not apt to fulfil simultaneously the function of a vibration damper or the function of an absorber of energy of shocks. Moreover, the hitherto known solutions of the problem have the drawback, in that a considerable change in their characteristics occurs due to changes in the ambient temperature or to an increase in the temperature of the absorber itself caused by the conversion of the absorbed energy into heat. At temperatures below -30.degree. C. absorbers lose their properties due to the solidification of the fluids or greases, whereas at temperatures above +30.degree. C. the viscosity of fluids and greases is lowered, which results in a decrease in the energy absorption capacity of the absorber.
In the hitherto known shock absorbing apparatuses the mechanical energy is absorbed by sets of steel springs, or pads made of vulcanized organic rubbers, while the vibration damping is accomplished by liquid media such as aliphatic alcohols, glycols, mineral and silicone oils, or various pastes based on resins, oils and mineral fillers.
For example, the absorber of very strong shocks, as described in the Polish patent specification No. 73,176, which is designed for rail vehicles, comprises two coaxial cylinders and a third cylinder which is being pushed between those two cylinders and which ends in an ellipsoidal ring of diameter greater than the distance between the coaxial cylinders. The shock energy is absorbed due to the deformation of the coaxial cylinders and to the friction of the ring. At lower shock energies this apparatus behaves as a rigid body, whereas at shock energies exceeding the permitted value the absorber is destroyed. Moreover, this absorber does not damp vibrations. The vibration damper, as described in the Polish patent specification No. 69,315, comprises two rings separated by an elastic pad. This apparatus is apt to damp vibrations, whereas the shock energy deforms the elastic pad which results in the necessity of replacing it.
The vibroisolators, as described in the Polish patent specification No. 83,615 with a viscotic vibration damper, comprise a cylinder and a plunger with a highly viscous liquid such as paraffin or silicone oil placed between them. This damper does not absorb shock energy, and at a higher amplitude and frequency of vibrations, the degree of damping is considerably lowered, in particular when using silicone oil as the damping medium.
The above-described hitherto known shock energy absorbers or vibration dampers fulfil only one strictly defined function and they are designed for strictly defined working conditions. Any deviations from these conditions result in the necessity for changing their design, applying other media for damping vibrations and absorbing the shock energy. A continuous transition from the function of an vibration damper to the function of a bump stop, and, further, to the function of a shock energy absorber is impossible of attainment in these hitherto known apparatuses. Moreover, in the hitherto known apparatuses it is impossible to obtain an increase in the energy absorptivity with an increase in the energy supplied for strong shocks repeating in short intervals of time and for vibrations with varying amplitude.
The apparatus according to the present invention is devoid of all these functional drawbacks and it can fulful simultaneously the function of a damper for vibrations with varying amplitudes and frequencies, of a bump stop, and of a shock energy absorber with its absorptivity increasing with the increase in the amount of energy supplied.
The combination of all the above mentioned functions and a continuous transition from one function to another is obtained in the apparatus according to the present invention due to the elaboration of an appropriate design of this apparatus and to the application of a viscoelastic medium with appropriately selected rheological properties as energy absorbing medium.